Scanning device for use in manufacturing implants

ABSTRACT

A scanning apparatus for controlling tool equipment used in production of implants, including a sensing device for sensing a contour of a model to obtain a selected representation based on the sensed contour, processing and controlling devices for receiving and processing the representation signals and for generating a signal array used for controlling of the tool and for controlling the sensing device so that the selected representation signals will ensure generation of the signal array allowing a high degree of accuracy in performance of the controlled tool equipment, wherein the sensing device includes a first device which is interactable with the contour and which displays, at its part interactable with the contour, a first form which substantially corresponds to a second form of a second device included in the tool equipment, with the first and second forms being substantially spherical.

TECHNICAL FIELD

The present invention relates to a device for generating, by means ofscanning applied to a scannable contour on a model, a representationwhich may be used for controlling a tool which operates with a highdegree of precision in connection with the production of a body, or atool for such a body, which is to be implanted in a human being. Asexamples of such bodies, mention may be made of dental implants, supportmembers, and the like. The model preferably consists of athree-dimensional model.

BACKGROUND OF THE INVENTION

It is known in the art, in the production of replacement parts, supportmembers and the like in the human body, to utilize a copy milling cutterin which a model is applied and sensed in the cutter and in response tothe sensing a tool processes a blank in order to produce from the blanka body or a tool part with the same shape as the model.

Our Swedish patent application No. 9003967-8 corresponding to U.S. Ser.No. 805,955 describes a system in which the sensing or scanning of themodel is separate from the processing equipment and control signals forthe latter are generated with the aid of computer equipment.

The use of copy milling cutters has its limitations regarding productionspeed. Moreover, these is an additional disadvantage in that theread-off function and processing function must be located in the samepremises. The appearance of the model is strictly linked to thestructure of the copy milling cutter, which means that variations andadditions to the shape of the model in question, enlargements of thecontours and the like cannot be put into effect with the desired freedomof choice.

In connection with equipment in which it is desired that the sensing andprocessing functions be located in different premises, it is importantthat an expedient read-off function and processing of the thus obtainedrepresentation is effected. The representation and the control must becapable of co-ordination so that unambiguous scanning and sensing can beadapted to an optimum or to the greatest possible extent minimizedcontrol signal function.

The quantity of read-off data/information should be kept to a minimum sothat the processing and selection functions in the computer equipmentmay be simplified/reduced while retaining the accuracy of control. Thescanning and sensing principles and storage function in the dataprocessing equipment are therefore of crucial importance in thiscontext.

In the case when a telecommmunications medium (for example,communication via the public telephone network) is to be employed totransmit information from one place to another, it is vital that thequantity of requisite control signals can be reduced. In addition tooperating with small scanning and processing quantities, it may berelevant to extract by means of data processing equipment characteristicparts of the read-off information and to transmit these characteristicparts via the medium, and also reconstruct replicas on the receptionside with the aid of these characteristic parts so that sufficientcontrol signals for the accurate control of the tool equipment can beobtained. In the scanning and sensing with contact devices/sensingsignals, it is also essential for the shape of the position in the partco-operating with the contour relate to the shape of that part of thetool by means of which a blank is processed. An optimum relationshipleads to significantly reduced read-off and processing information.

It is also esssential for the sensing and control functions to berelated to one another without increasing processed data or informationin the data processing equipment. A relationship between reading-in andreading-out of information entered in the computer must also beestablished in such a manner that, for example, the read-off functionwill be separated from the read-in function so that the processingfunction can be carried out more quickly than the read-out function.

The tool equipment must, for example in the production of dentalimplants, bridges, etc., be capable of working to a degree ofaccuracy/tolerance of one or a few hundredths of a millimeter, (forexample, 0.01-0.09 mm). The resolution on scanning may in one embodiment(for example, scanning by laser) be appreciably greater, for example,one or a few thousandths of a millimeter.

SUMMARY OF THE INVENTION

One object of the present invention is to solve the above-outlinedproblems by providing a novel problem structure of an apparatus in whicha representation may be entered into computer equipment which generatesa signal array that effectuates or is included in the control of thetool equipment, and the sensing and/or a selection function effectuatedby the computer equipment of the representation is or are selected so asto ensure an order of magnitude of the signal array which satisfies thedegree of accuracy with which it is expected that the tool equipmentwill perform.

In one embodiment, the sensing means operates with a first memberco-operating with the contour, for example, a needle. At its portionco-operating with the contour, the member displays a first form whichsubstantially corresponds to a second form of a second member which isincluded in the tool equipment and which interacts, with a portioncarrying the second form, with a blank in the production process. Theportion may consist of a milling cutter. In one embodiment, the firstand second forms are substantially spherical. In addition, the sensingfunction and the processing function of the tool equipment are mutuallyco-ordinated so that a linear transmission function arises. The sensingfunction and the processing function may then operate at differentspeeds. It is thus of interest in this art that the speed of theprocessing function may exceed the sensing function.

The computer equipment is preferably designed with memory means in whichthe representation or information of significance for the representationis stored. The memory may, for instance, consist of a magnetic internalor primary memory of the RAM type. In that case when information is tobe stored, a secondary memory may also be employed. Such secondarymemory may be of the permanent magnet type. The read-in function of theinformation is then preferably separated from its read-out function sothat, for example, control signal generation may be carried out morerapidly than the read-in of the representation.

In one embodiment, the present invention will comprise a contour sensingportion interactable with the contour and having a curved surface whichmay be brought into abutment against the surface of the contour. Thedimensions of the curved area, for example a spherical area, are to beput into relation with the details of the contour so that a reducedsensing degree (resolution) is obtained.

In one embodiment, the sensing function takes place on models of soft orbrittle material, for example plaster. With the aid of the toolequipment, bodies or tool parts may be made completely or partly ofhard, soft or brittle material.

In one embodiment, compression takes place in the computer equipment offirst information referable to the representation on the formation ofsecond information referable to control of the tool equipment. The firstand/or second information may be stored in storage devices on delayedtransmission of the control information, for example via atelecommunications medium (for example the public telephone network).The storage devices may then be designed with a capacity which entailsstorage of the information from sensing of one or more contours. In oneembodiment, the storage devices have a capacity of at least 2-3megabyte.

In one embodiment, the sensing is carried out during rotation of themodel with simultaneous mutual relative displacement between the modeland a sensing device. The sensing function is executed a large number oftimes per revolution, for example, 360 times per revolution. Therelative displacement may be selected to be approximately 0.1mm/revolution. Only characteristic parts of the representation and/orcontrol can, in one embodiment, be transmitted on the employedtelecommunications medium. A replica of the control/control signals isgenerated at a reception point with the aid of the characteristic parts.

The present invention also utilizes known mathematical principles in thecompression function.

As a result of the proposals disclosed in the foregoing, a considerablereduction may be achieved in the quantity of information which isobtained in the sensing function. The capacity and space on the computerequipment may then be kept to a minimum, at the same time astransmission via the relevant link is simplified/shortened in terms oftime. The sensing and control signal-generating functions may be keptseparated and processed independently of each other. A plurality ofsensing stations may be connected to the same computer equipment andsimilarly a-plurality of sensing and computer equipment units may beconnected to one and the same tool equipment via the same or differentconnections. The information quantities may be reduced substantially,which gives short processing times in the computer equipment andtransmission of a relatively small quantity of control information. Theproposed principles also afford the possibility of so-calledcontact-free sensing in which the sensing function more exactly and ingreater detail senses the contour in question. The representationobtained from the sensing function can be reduced/compressed in thecomputer equipment with the aid of the selection function. As a resultof the proposed spherical shape of the abutment portion of the sensingdevice against the contour, sensing of soft and/or brittle models can becarried out. Since the shapes of the sensing and processing device aredesigned to be substantially identical, complicated calculated functionsreferable to the actual and sensed contour of the model in question areeliminated. As a result of the proposed structure, the processingcapacity in the computer equipment may be reduced by one third andsavings of the space/volume of the computer equipment may be reduced byup to one fifth.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

One currently preferred embodiment of an apparatus which displays thecharacteristic features of the present invention will be described ingreater detail hereinbelow, with particular reference to theaccompanying Drawings, wherein

FIG. 1 shows in a block diagram form the structure of the sensing devicewith computer equipment (PC), programmable input and output circuits,control unit for signal emission and signal sensing units in which thesignal emitting unit controls a model carrying unit so that this movesin relation to a sensing unit that emits signals to the signal sensingunit;

FIG. 2 shows, on a larger scale and from the side, how a sensing portionin a sensing unit interacts with the contour of a model;

FIG. 3 shows from the side how a blank is processed by means of a toolequipment part, by means of which the contour in FIG. 2 is produced fromthe blank on reduced, equal or enlarged form;

FIG. 4 shows on a larger scale the interaction between the sensingportion and the contour of the model; and

FIG. 5 shows in a table form how the sensing proceeds in the embodimentaccording to FIG. 4.

DETAILED DESCRIPTION OF EMBODIMENT

Referring to the Drawings, in FIG. 1 a read-off device is givenreference designated as 1 and comprises among other things, a mechanicalunit 2 on which a model 3 may be secured on a rotatable device 4. Inaddition to being rotatable in the direction of the arrows of rotation 5(counter-clockwise and clockwise) about an axis of rotation 6 by meansof a drive motor 7, the device 4 and the drive motor 7 arelongitudinally displaceably disposed in the directions 8 of the axis 6.By this means, the model 3 will also be longitudinally displaceablydisposed in the directions 8. The longitudinal displacements arerealized by means of a motor 9. A sensing unit 10 which is fixedlydisposed in relation to the model is provided with a device 11 which maybe resiliently brought into contact with the contour 3a of the model 3.When the model is turned and displaced in relation to the unit 10 andthe device 11 in connection with the activations of the motors 7 and 9,these will be received from the output of the unit 10 a representationin response to sensing by the device 11 of the contour 3a, therepresentation being in the form of one or more electric signals i1. Thelatter signal or signals are processed in a signal processing unit 12where the representation i1 is sampled and digital signals i2 areobtained from the output 12a of the unit 12 in response to thesamplings. The digital signals can be transmitted on a bus connectionfor parallel transmission of 16 bits. The unit 12 is, via the busconnection, connected to a control unit 14. The motors 7, 9 arecontrolled by means of a combined unit 15 for driving, speed adjustmentand positioning of the motors. The control functions for the motorsoperate with feedback function and the control and feedback conductorsare indicated by reference numerals 16, 17; and 18, 19, respectively,and the set and actual value signals are indicated by i3, i4; and i5,i6, respectively. The unit 15 is connected via inputs and outputs 15a tothe control unit 14. The connection is designed as an additional busconnection 20 for 16-bits parallel transmission. The control unitcomprises first and second units 14a and 14b which serve units 12 and 15respectively. Control of the motors 7 and 9 is related to the sensingand the representation i1 for this.

The sensing device includes a programmable interface 21 with read-in andread-out devices which are connected to the control unit 14 via a busconnection 22 for 24-bits parallel transmission. A data processingequipment, for example a PC 23, is connected to the read-in and read-outdevices 21 via a bus connection, for example an AT bus connection. ThePC may be of AT-286 type which includes one or more magnetic internalmemories or primary memories of the RAM type. The computer 23 is alsofitted with a secondary memory 26, 27 of the permanent magnet type. Amemory 26 may consist of a hard disk and a memory 27 of a floppy disk.

The signals on the bus connection 20 are shown with reference numerali7, on the bus connection 22 with i8 and on the bus connection with i9.The computer 23 is connected to or provided with a data communicationport 28 via which the control/representation information may be enteredinto and retrieved from the read-off device via an input and output 28ato and from another data processing equipment or data communication (notshown). Moreover, the computer 23 is connected to a modem 29 via whichthe computer may be connected to a telecommunication connection 30 in atelecommunications network, for example the public telephone network.Information to and from the connection 30 via the modem 29 is indicatedby reference numerals i12 and i13 respectively.

The software which is employed in the computer may be of known type. Inthe present case, the following are employed:

User program

Program for text and calibration

Program for file handling

Program for data compression

Program for data communication

Program for automatic call up/transmission via the modem on thetelecommunications network, single/multiple file program.

FIG. 2 shows the device 11' sensing the contour 3a' of the modelmagnified in relation to FIG. 1. The resilient abutment of the device11' against the contour is effectuated by spring means 31. The unit 10'is securely disposed in relation to the device 11'. The latter isdesigned with an abutment portion 32 which is preferably substantiallyspherical in the illustrated case. The spherical shape is indicated byreference numeral 33.

In FIG. 3, a blank is indicated by reference numeral 34. The blank,which may be of titanium, cemented carbide, alloy, graphite, and thelike, must be provided with a contour 3a and 3a' in FIGS. 1 and 2corresponding to contour 3a'. The blank 34 is processed or treated witha tool 35 which, in the present embodiment, consists of a millingcutter. The forward portion 36 of the tool has a shape 37 whichsubstantially, preferably exactly, agrees with the shape 33 of theread-off device 32 according to FIG. 2. The tool/milling cutter isdisposed in a known manner in a spindle and the tool includes a tooladjustment control portion 38 which receives control signals i14 via thetelecommunication connection 39 (see 30 in FIG. 1) and a modem 40 whichinteracts with the modem 29 according to FIG. 1. Via the modem 40,control signals i14' are fed to the control portion 38.

FIGS. 4 and 5 show the read-off principle, read-in and read-out into andfrom, respectively, the memory of a computes of sensed values andentered values V, respectively. The model 3'" is rotated about its axis6' and sensing takes place in different angles) ρ. In the example,sensing takes place for each degree, that is, 360 times per revolutionand the read-off angles are indicated by 0-360. The read-off points aresymbolized by reference numeral 41. For each revolution (360), the modelmoves in a Z direction in relation to the read-off portion 33', 33",these positions each representing their location in relation to themodel 3'". For every revolution that the model rotates, a relativemovement S (=pitch) between the model and the sensing portion in thepresent embodiment is 0.1 mm. In the table according to FIG. 5, thepitch Z for each degree ρ is 0.1 mm/360. Other pitches S and number ofsensing points may be employed within broad limits.

In the table IS indicates a read-in sequence in the memory of thecomputer and US a read-out sequence from the memory. V representsread-in/readable value for each degree. The values V occur in binaryform or other suitable form. The sequences IS and US can be executed ina known manner at different speeds. The sequence US is preferably higherthan the sequence IS.

The sensing surface 33 of the sensing portion 32 displays a radius Rwhich may lie within the range of between 0.5 and 2.0 mm and ispreferably 1.0 mm. This size of the radius is suitable in productionfrom models which represent a dental implant, bridge, and the like. Thesensing surface 33 is thus selected so as to give a reduced sensingdegree/resolution in relation to the true detailed shape of the contour.

One method of compressing the entered data quantity is to approximate anumber of points by means of a function, for example, a polynomer of thethird degree (c₁ +c₂ x+c₃ x² +c₄ x³). The total computer quantity isdivided into groups. Each such group is approximated by a function. Soinstead of transmitting pure measurement data from the read-off unit toa relevant factory computer, the coefficients of the function aretransmitted for each group (c₂, c₂, c₃ and c₄ in the case employing apolynomer of each degree).

Since both functional value (indicator signal) and the distance betweeneach read-in is known, that is f (x) and x in each group when thefunction is a function of a variable, the function may be approximatedby the least square method. The solution in the sense of the leastsquare method to the above equation system Ac=f is given by the solutionto the equation system Au^(T) Ac=A^(T) f. If Q(x) is the indicatorsignal at a given position and f(x) is the approximated value at thesame point, the error can be calculated with error(x)=f(x)·Q(x). Thenumber of values included in each group to be approximated by a functionmust be adapted such that the error (error(x)) is less than the largestpermitted error for all values in the group. The above mathematicalprocessing is carried out in the computes in a known manner.

The present invention should not be considered as restricted to thatdescribed above and shown on the drawings, many modifications beingconceivable without departing from the spirit and scope of the appendedClaims.

We claim:
 1. A scanning apparatus for controlling tool equipment used inproduction of three-dimensional bodies such as human body restorations,comprising:sensing means for sensing a contour of a model to obtainselected representation data based on said sensed contour in the form ofat least one signal, said sensing means being located at a first site;movement effecting means for effecting rotational movement of said modelsimultaneously with relative displacement movement between said modeland said sensing means while said sensing means simultaneously sensingthe contour of the model, said movement effecting means being actuatedand controlled by a control unit; processing and controlling means forreceiving and processing said representation data signals and forgenerating sensing control signals used for controlling a sensingfunction of said sensing means; computer equipment for obtaining inputsignals based on said processed representation signals and forgenerating output signals to be used in controlling of said toolequipment; means for controlling operation of said tool equipment at asecond reproduction site; means for transmitting output signal data fromsaid first site to said second reproduction site.
 2. The apparatus asclaimed in claim 1, wherein the sensing means and said tool operationcontrolling means are designed to perform in a substantially coordinatedmanner.
 3. The apparatus as claimed in claim 1, wherein the sensingmeans and said tool operation controlling means operate at differentspeeds.
 4. The apparatus as claimed in claim 1, wherein an informationsignificative of the representation is storable in a memory of thecomputer equipment.
 5. The apparatus as claimed in claim 4, wherein saidmemory includes at least one of an internal (primary) memory of the RAMtype and a secondary memory of the permanent magnet type, and whereinthe reading-in of said information is separated from its reading-out. 6.The apparatus as claimed in claim 1, further comprising means forrotation of the model with simultaneous mutual relative displacementbetween the model and the sensing means when the sensing means sensesthe contour, and wherein the sensing takes place a large number of timesper revolution.
 7. The apparatus according to claim 1, wherein saidsensing takes place about 360 times per revolution, and said relativedisplacement is about 0.1 mm/revolution.
 8. The apparatus as claimed inclaim 1, wherein the sensing means is connected to the computerequipment via an interference comprising programmable input and outputcircuits, which are connectable to said processing and controlling meansincluding said control unit which is connected to a signal generationunit for a model movement actuating means and to a unit converting theshape of the contour into electrical signals.
 9. The apparatus asclaimed in claim 1, wherein the sensing surface of the sensing portiondisplays a radius (R) in the range of between 0.5 and 2.0 mm tocooperate with a model which represents a dental implant, bridge and thelike.
 10. The apparatus as claimed in claim 1, wherein said sensingmeans includes a first device which is interactable with the contour andwhich displays, at its part interactable with the contour, a first formwhich substantially corresponds to a second form provided on a seconddevice included in the tool equipment, said first and said second formsbeing substantially spherical.
 11. A scanning apparatus according toclaim 1, wherein said sensing means is positioned at an angle withrespect to a longitudinal axis of said model.
 12. A scanning apparatusaccording to claim 11 wherein said tool equipment is positioned at anangle with respect to a longitudinal axis of said blank.
 13. Anapparatus for controlling tool equipment used in manufacturing at leastone three dimensional body, comprising:sensing means including a sensingdevice for sensing a contour of a model of an implant to obtain arepresentation of said contour in the form of at least onerepresentation electrical signal; said sensing means including means foreffecting rotational movement of said model simultaneously with relativedisplacement movement between said model and said sensing device whilesimultaneously sensing said contour; a signal processing unit forprocessing said representation electrical signals to obtain digitalsignals; a control unit for controlling operation of said signalprocessing unit and said sensing means; and data processing equipmentfor receiving signals from said control unit and for generating controlsignals used for operating said tool equipment; wherein said sensingmeans includes a first member which is interactable with the contour ofthe model during said sensing and has at its part interactable with thecontour of the model a first form which is the same as a second form ata part of a second member provided in said tool equipment which isinteractable with a blank in production of said three dimensional body;wherein said sensing means is inclined at a first angle with respect toa longitudinal axis of said model, said tool equipment is inclined at asecond angle with respect to a longitudinal axis of said blank, andwherein said first and second angles of inclination are substantiallythe same.
 14. An apparatus according to claim 13 wherein said first andsecond forms are spherical.
 15. An apparatus according to claim 13,further including a programmable interface including read-in andread-out devices connected between said control unit and said dataprocessing equipment.
 16. An apparatus according to claim 15, whereinsaid data processing equipment includes a computer with at least oneprimary magnetic memory of the RAM type.
 17. An apparatus according toclaim 16, wherein said computer is also provided with a secondary memoryof a permanent magnetic type.
 18. The apparatus as claimed in claim 15,wherein the read-in or read-out data quantity is compressed by means ofan approximation of a quantity of read-in or read-out points with afunction which is a polynomer of the third degree.
 19. The apparatus asclaimed in claim 18, wherein the read-in or read-out data quantity isdivided into groups; each respective group is approximated with afunction; and the coefficients of each respective function aretransmitted between relevant communication parts, including from theread-out unit to a computer, at the reproduction site as representationof the total quantity of read-in or read-out data.
 20. The apparatus asclaimed in claim 19, wherein the error between an actual indicatorsignal and each respective approximate value is calculated, and also thenumber of included values in each respective group of said groups whichis to be approximated with a function will be adapted such that anabsolute value error is less than the largest permitted error for allvalues in the group.
 21. The apparatus as claimed in claim 13, whereinthe speed of the processing and controlling units exceeds that of thesensing means.
 22. The apparatus as claimed in claim 13, wherein a firstinformation data referable to the representation is compressed in thedata processing equipment on formation of a second data informationreferable to the control of the tool equipment, and wherein at least oneof the first and the second information may be storable in a storagemeans in order to realize a time lag between at least one of the sensingand controlling functions in relation to a transmission of thecontrolling signals to the data processing equipment.
 23. The apparatusas claimed in claim 22, wherein said storage means stores therepresentations for one or more contours for transmission via atelecommunications medium at off-peak hours thereon, and wherein saidstorage means have a capacity of at least 2-3 megabyte.
 24. Theapparatus as claimed in claim 13, wherein the sensing surface of thesensing device is selected to provide a reduced sensingdegree/resolution in relation to the true detailed form of the contour.25. A scanning apparatus for controlling tool equipment used inproduction of three-dimensional bodies such as human body restorations,comprising:sensing means for sensing a contour of a model to obtainselected representation data based on said sensed contour in the form ofat least one signal; processing and controlling means for receiving andprocessing said representation data signals and for generating sensingcontrol signals used for controlling a sensing function of said sensingmeans; computer equipment for obtaining input signals based on saidprocessed representation signals and for generating output signals to beused in controlling of said tool equipment; and movement effecting meansfor effecting rotational movement of said model simultaneously withrelative displacement movement between said model and said sensingdevice while simultaneously sensing the contour of the model, saidmovement effecting means being actuated and controlled by a controlunit; and wherein characteristic parts of the representation and thecontrol are selected prior to the transmission on a telecommunicationsmedium; and wherein a replica is generated at a reception site based onthe characteristic parts of the representation.
 26. A scanning apparatusfor controlling tool equipment used in production of three-dimensionalbodies such as human body restorations, comprising:sensing means forsensing a contour of a model to obtain selected representation databased on said sensed contour in the form of at least one signal;processing and controlling means for receiving and processing saidrepresentation data signals and for generating sensing control signalsused for controlling a sensing function of said sensing means; computerequipment for obtaining input signals based on said processedrepresentation signals and for generating a controlling signals array tobe used in controlling of said tool equipment; and movement effectingmeans for effecting rotational movement of said model simultaneouslywith relative displacement movement between said model and said sensingdevice while simultaneously sensing the contour of the model, saidmovement effecting means being actuated and controlled by a controlunit; and wherein a first information data referable to therepresentation is compressed in the computer equipment on formation of asecond data information referable to the control of the tool equipment,and wherein at least one of the first and the second information may bestorable in a storage means in order to realize a time lag between atleast one of the sensing and controlling functions in relation to atransmission of the controlling signals to the computer equipment.